Weston brake hoist construction



p 3, 1968 c. s. SCHROEDER 3,399,867

WESTON BRAKE HOIST CONSTRUCTION Filed Oct. 28, 1966 s Shets-Sheet 2 INVENTOR.

TTTTTTTTTTTTTTTTTTTTTTTTTT ON Tlcl i 17 5 CSSCQQZL United States Patent Yale & Towne Inc., Cleveland, Ohio, a corporation ofv Ohio Filed Oct. 28, 1966, Ser. No. 590,331 3 Claims. (Cl. 254-168) ABSTRACT OF THE DISCLOSURE A hoist is equipped with a Weston brake through which a drive shaft controls lifting and lowering movements of a load sheave, and the pawl of the Weston brake is frictionally mounted on a shaft portion of the load sheave. When starting to rotate in load lifting direction, the sheave moves the pawl away from the Weston brake ratchet so that the pawl need not vibrate while the lifting continues. When rotating in lowering direction, the sheave moves the pawl to holding position against the ratchet so that the lowering may be controlled through slipping of the brake while the sheave slips relatively to the pawl.

My invention relates to a hoist of the type that utilizes a Weston brake mechanism, and more particularly to a novel construction for operating parts of the hoist.

Those persons skilled in the art will understand that the Weston brake mechanism of a hoist is equipped with a disc that is held against rotation in a load lowering direction, as by a pawl engaging ratchet teeth on the disc. Lowering movements of the hoist are effected through the slipping of a clutch disc relatively to the disc that is held. The discs will not slip when the hoist lifts the load and both discs then will rotate, as will be permitted by the pawl. Thomas Weston developed the concept many years ago and showed it in several patents, one of those being No. 320,317 dated June 16, 1885.

The industry continues to use the Weston concept as an effective means of controlling the movements of a hoist and there are many later patents, for example No. 2,503,682, that mention a Weston brake. Nevertheless, the pawl of the brake frequently does not contribute the service and operation that is necessary, and no one until the present time, so far as I am aware, has been able to equip a hoist of this type with a pawl arrangement that is fully satisfactory. Through the novel contribution of my invention, I am able to achieve more effective action of the pawl of a Weston brake on a hoist. Also, the mechanism that operates the pawl will have considerably longer life than the pawl operating mechanisms of the prior art.

In the earlier mechanisms, the pawl generally is pressed by a compression spring or by a torsion spring toward the ratchet teeth on the Weston mechanism. Obviously, the pawl will move back and forth during a lifting operation, with each back and forth movement requiring a yielding and then a recovery of the spring. It has been proposed to use a spring that binds on the surface of a ratchet, but that spring is subject to wear and again must yield with movements of the pawl. A pawl that is used on a hoist will accept the load, and it naturally is important that the Pawl should not fail. Yet the movements of the types of spring I have mentioned will result in deterioration of the pawl spring and, eventually, its destruction.

As an important feature of the invention that I have now conceived, I employ yielding means through the intermediary of which the load sheave of the hoist will move the pawl relatively to the ratchet teeth. When starting to rotate during a lowering movement of the ice hoist, the load sheave will move the pawl toward the ratchet teeth, and the yielding means will merely yield when the pawl is against the ratchet. When the load sheave rotates in a lifting direction, it will move the pawl away from the ratchet.

As a preferred feature, I arrange frictional surfaces between the pawl of the Weston mechanism and the load sheave. A spring holds the frictional surfaces in coacting relation so that the pawl will rotate with the sheave, but nevertheless enabling the sheave to rotate after the pawl encounters a stop. The stop at one side will be a surface of the ratchet, and at the other side the stop may be a surface on a fixed part of the hoist. Thus, as a feature of my invention I move the pawl of a Weston mechanism through the intermediary of means that comprise frictional surfaces. The spring that I utilize need have little or no yielding movement, and thereby the life of the spring will be very much extended.

As a further feature, I utilize in the hoist a load sheave that has a central bore. I mount the pawl of a Weston mechanism for rotating movement on a portion of the load'sheave, while arranging the drive shaft of the hoist within the bore of the load sheave, enabling me to contribute a very compact and effective drive.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of my invention, in order to prevent the appropriation of my invention by those skilled in the art.

Referring now to the drawings:

FIG. 1 shows a horizontal section of a hoist that utilizes my invention.

FIG. 2 shows a section on the line 2--2 in FIG 1.

FIG. 3 shows a perspective view of my novel pawl arrangement.

FIG. 4 shows a section on the line 44 in FIG. 1.

For the purpose of describing my invention, I show in FIG. 1 of the drawings a hoist casing 10 that is much like the one which is shown in the copending application of George F. Quayle, Ser. No. 590,366, entitled Casing for Hoist. The details of casing 10 actually are not important here, and it is merely necessary to know that casing 10 has opposed end walls 11, 12 and a medial wall 13, and that there is a hoist motor 14 on the wall 12 of the casing. As best seen in FIG. 4, a hoist support book 15 is attached through suitable means to the top of casing 10. In the casing 10 is a load sheave 18, which I shall describe, for operating chain 16 that extends through an opening in the bottom of the casing and that is equipped with a load hook 17.

In FIG. 1, it will be seen that I mount the load sheave 18 to rotate in the axis of motor shaft 21, utilizing bearings 19, 20 that are supported in openings of easing walls 12, 13. The sheave 18 has a central bore 22, and I form the inner end of sheave 18 with a hollow shaft portion 23 extending a considerable distance past the medial casing wall 13.

I utilize a hoist drive shaft 24 that is arranged in the bore 22 of the load sheave, connecting that shaft to motor shaft 21 as by a spline 25. As shown, drive shaft 24 is supported at one end on motor bearing 26, and has clearance whereby there will be no direct transfer of forces between shaft 24 and bore 22. The opposed end portion of drive shaft 24 extends beyond the hollow shaft portion 23 of sheave 18 and has fixed upon it a drive pinion 27 that rotates in a bearing 28 on the casing wall 11.

The drive pinion 27 meshes with gear teeth on a disc 29 of a Weston brake mechanism, that I indicate generally by the numeral 30. Shaft 31 of Weston mechanism is mounted to rotate in bearings 32, 33 on the casing walls 11, 13 and is formed with gear teeth 34 meshing with a gear 35 that is keyed to the load sheave 18. As will be seen, the hoist motor 14 will act through the Weston mechanism 30 to control the lifting and lowering movements of the chain 16 on load sheave 18.

Now, I call attention to the holding pawl 36 that coacts with the ratchet disc 37 of Weston mechanism 30, as is well shown in FIGS. 1, 2 and 3. In my invention, I form the pawl 36 with an opening that is assembled on the hollow shaft portion 23 so as to mount the pawl for rotation on the load sheave 18. I equip shaft portion 23 with a washer 38, FIG. 1, that is arranged at one side of holding pawl 36, with the washer held in position by a retaining ring 39, for example. In effect, washer 38 forms a flange on the portion 23 of the sheave. I assemble a coil spring 40 in position about the shaft portion 23, between the opposed side of pawl 36 and a washer 41 that lies against one side of gear 35. The opposed ends of spring 40 press against washer 41 and against pawl 36, in

effect acting between the load sheave and the pawl to hold the pawl in frictional relation to the washer 38 on the sheave portion 23. Thus, when free to do so, holding pawl 36 will rotate with the load sheave 18. I have found that no partciular frictional material is necessary to achieve the pawl operation. The frictional surfaces may simply be plain steel surfaces on pawl 36 and washer 38, though I do not wish to be so limited.

When considering the relation between the operating parts that I have described, it will be seen that the load sheave 18 will move the holding pawl 36 toward the ratchet disc 37 when the hoist moves in a load lowering direction, and away from that disc when the hoist moves in lifting direction. As is illustrated by the full line holding position of the pawl 36 in FIG. 2, the toothed surface 37a of ratchet disc 37 will act as a stop for one direction of movement. In the opposed direction of movement, a surface 42 on a part of the hoist will act as a stop for pawl 36, as illustrated in FIG. 3 and in dot-and-dash lines in FIG. 2. While pawl 36 is against stop surface 42, there will be clearance whereby the pawl will have no contact with the teeth of ratchet disc 37 as the disc rotates. After the load sheave 18 has moved pawl 36 to stop position, the pawl naturally can move no farther in the particular direction, but the hoist may continue to operate because load sheave 18 is able to rotate through slipping of the frictional surfaces between pawl 36 and washer 38.

It will thus be seen that the holding pawl 36 will have merely one movement, that being away from ratchet 37, during a lifting operation of the hoist. Of course, pawl 36 moves at the appropriate time to holding position. Those movements of pawl 36 are effected by an operating part of the hoist acting through the intermediary of means that will yield when pawl 36 is in a stop position, but the yielding is contributed through frictional surfaces and the coil spring 40 need not yield. Thereby spring 40 need accept no stresses that would shorten its life, while I also reduce very greatly the wear that may take place between holding pawl 36 and the teeth of ratchet disc 37.

It is conceivable that the holding pawl 36 of my novel construction may be mounted on an operating part other than the load sheave 18, for operation by that part. However, I do prefer to mount the pawl 36 relatively to sheave 18, as I have described, because the load that is accepted by the pawl, and also the forces that operate the pawl, then will be applied in more direct relation to the load on the hoist.

I have not described the details of the Weston brake 30 because those details may be conventional. However, I shall indicate that brake 30 includes a clutch disc 43 that is integrally mounted on shaft 31, and that is in screwthreaded relation to the disc 29 that I have mentioned. The ratchet disc 37 is rotatably mounted in position between discs 29, 43 so as to be gripped by those discs during a load lifting operation, or for holding the load.

I believe that those persons skilled in the art will now understand that the novel contribution of my invention enables me to achieve much more effective and reliable operation of a hoist, when that host is of the type that utilizes a Weston brake. Moreover, I enable the hoist to be constructed in a form that is relatively small and compact. I believe, therefore, that the very considerable merits of my invention will be fully appreciated.

I now claim:

1. In a hoist of the type having a load sheave and a Weston brake mechanism mounted to rotate in axes that extend longitudinally in spaced relation to each other in a hoist casing, said Weston brake mechanism including a clutch disc geared to the load sheave and at times slipping relatively to a ratchet disc that is held by a pawl which engages teeth on the periphery of the ratchet disc, there being a reversible hoist motor for actuating the brake mechanism to effect lifting and lowering rotation of the load sheave, the improvement that comprises a portion on said load sheave extended in the sheave axis so as to lie in position relatively near the ratchet periphery, means mounting the ratchet holding pawl on said extended portion of the load sheave while permitting said sheave portion to rotate relatively to the pawl, and yielding means through the intermediary of which said portion of the sheave acts to move the pawl into and out of holding relation to the ratchet teeth incidental to rotating movements of the load sheave, said yielding means yielding to permit the clutch disc to slip during lowering rotation of the load sheave.

2. A construction as set forth in claim 1, in which said portion of the load sheave is equipped with a flange in opposed relation to a side surface on the pawl, and a spring acting in an axial direction against the pawl to press said surface into frictional contact with the flange.

3. A construction as set forth in claim 2, in which the load sheave is hollow, and including a drive shaft connected to the hoist motor and assembled in the ho]- low sheave and its extended portion, said drive shaft having a portion extending beyond the sheave portion on which the pawl is mounted, and gear means connecting said portion of the drive shaft to the Weston brake mechanism.

References Cited UNITED STATES PATENTS 1,745,205 1/1930 Bryant 254- 2,243,358 5/1941 Robins 254-168 2,244,221 6/1941 Schroeder 254-168 RICHARD E. AEGERTER, Primary Examiner.

H. C. HORNSBY, Assistant Examiner. 

